1. Field of the Invention
The present invention relates to a gas laser device having a function for discriminating a type of alarm generated in a laser oscillator.
2. Description of the Related Art
In the prior art, when an alarm is generated in a gas laser processing device having a laser oscillator in an operable state, a command for stopping discharge is transmitted to a laser power supply for safety purposes. In this regard, as a preparation for restoring the laser oscillator, the pressure of laser gas within a discharge tube of the oscillator is controlled so as to be decreased. This is because it is necessary to sufficiently reduce the gas pressure in order to initiate discharging when restarting the laser oscillator.
As a relevant prior art document, for example, JP 2008-306110 A discloses a start-up method for a discharge-excited gas laser unit, in which laser gas is circulated within a laser discharge tube, and a laser is generated by high-frequency discharge. This method includes the steps of: previously storing an output current characteristic, as a normal current characteristic, of a DC power supply part of a laser power supply unit of the gas laser unit when the gas laser unit is normally activated; detecting an output current of the DC power supply part of the laser power supply unit while the gas laser unit is activated; and controlling the pressure of the laser gas within the laser discharge tube such that the detected output current of the DC power supply part does not exceed a threshold which is determined based on the normal current characteristic (claim 1, etc.).
On the other hand, JP 2011-222586 A discloses a gas laser oscillator including: a power output command section for generating a power output command by superposing pulses at a head of each step, a voltage application section for applying a voltage to a discharge tube based on the power output command, a discharge tube voltage detection section for detecting a voltage of the discharge tube, a discharge tube monitoring section for monitoring the voltage of the discharge tube, and a discharge start judging section (CNC) for judging that discharging has started when difference between the change ratio of the voltage of the monitored discharge tube for the power output command and a change ratio of voltage of the discharge tube for the power output command that is predetermined based on data obtained during normal discharge in the discharge tube falls within a predetermined threshold value.
In the invention of JP 2008-306110 A or JP 2011-22586 A, the initiation of discharge in the laser oscillator can be judged even in the high gas pressure close to the pressure in the laser operation state, whereby the laser oscillator can be safely initiated in a relatively short time. However, in such a gas laser device, it is desired that a restoration time, from when the alarm is generated to when the laser oscillator is returned to the operable state, be reduced, and that an amount of consumption of laser gas, used to increase the laser gas pressure to the high pressure (or the pressure of the laser operation state) after the laser gas pressure is decreased for discharging, be reduced.